Connective Tissue Notes (PDF)

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W notes Connective tissue  Istronsense offf madeupof Connective tissue Hmm Nfffhfgythaai MM M1 3 othercomponents d 1 ifff dyi f i f.  always beneath an Connective tissue epithelium GTA Support tissue - provides structural on Collagen fiber Ée and metabolic support to epithelial, d Fibroblast muscular and nervous tissue, as well as other connective tissues (adipose, blood, bone and cartilage). Adipocyte Vascularized tissue - with blood and lymphatic vessels that contribute to the Elastic fiber nutrition and elimination of waste from all tissues. Participates in the defense, protection and repair of the body. onnel tissue the It is composed of: Reticular fiber  Cells Pericyte Blood vessel  Extracellular matrix a lotunlike epithelial Extracellular matrix (ECM) The extracellular matrix (ECM) is a complex of macromolecules manufactured and secreted by cells into the space between them. In connective tissue there is a large amount of ECM with a limited number of cells scattered in it. The ECM has two main components: Ground substance Fibers  haswater very important GAG ECM: Ground substance one of the components Amorphous gelatinous material constituted by water and three other components: - Glycosaminoglycans (GAG) - Proteoglycans - Structural glycoproteins below explained Glycosaminoglycans (GAG): Long chains of disaccharides that repeat themselves The main GAGs found in the matrix are sulfated. The only unsulfated GAG is hyaluronic acid, which is also the largest of them. The sugars that form these GAG are negatively charged, so they attract positive charges such as the Na+ ion. High Na+ concentrations will attract large amounts of water (tissue fluid). due the positive charges to Negative charges cause the GAG chains to repel each other, adding viscosity to the matrix and the water content will make the matrix very resistant to compression. Proteoglycans: When GAGs bind to a protein (nuclear protein) they form a proteoglycan. There are many types of proteoglycans of very different sizes. Hyaluronic acid can bind numerous proteoglycan molecules forming an aggregate. formedwhen hyaluronic acid binos proteoglycans  bindepitheliato connective tissue Glycoproteins : bybinding to Structural integrins in the basement membrane Proteins bound to branched polysaccharides They have binding sites for various components of the ECM PORTANT Anchor the epithelia to the matrix (binding to integrins) J Union between the elements of the matrix (collagen fibers and Thatthe proteoglycans) natural proteins lyco do ECM: Fibers other one of the main of components ECM Provide tensile strength and elasticity to the tissue. There are two different types of fibers in the connective tissue:  Collagen  Elastin 11hpm here.ie most abundant Collagen type 1  non elastic Collagen fibers resistant to traction most abundant Non elastic, hard and firm protein The most abundant of all the proteins in the body Forms fibers that are very resistant to traction According to its amino acid sequence, there at least 35 different types of collagen Collagen biosynthesis Fibroblasts Ground Substance synthesized Tropocollagen polymerization Procollagen goes ecM Ayillagen Collagen Fibroblasts synthesize the collagen precursor molecule, procollagen, and release it to the ECM. There, it is activated becoming tropocollagen.  Tropo collagen fibrils assembled micro microfibrils assembled fibril The tropocollagen molecules are fibril assembler Collagenfibers assembled spontaneously, always in the Ifthereisnotenough vitaminc head-tail direction and in a regular and fiberswill tear thetropo collagen staggered manner. bleedingoccurs These assembled molecules form the collagen microfibrils. When several microfibrils are associated, they form a fibril of collagen. Several fibrils will form the collagen fiber. The union between the molecules of tropocollagen requires the presence of vitamin C. A vitamin C deficit will create unstable chains and they will not be able to be added to form the fibers. Therefore, there will be tissues that become fragile, and bleeding occurs due to capillary ruptures (scurvy).  Collagen types Type I: it is the most abundant. It is synthesized by fibroblasts and also by osteoblasts. Very resistant to tension forces. It appears in most of connective tissues: skin (dermis), tendons and ligaments, organ capsules, bone... Type II: appears only in the cartilage. It is synthesized by chondroblasts and is very resistant to stress. Type III or reticular fibers: It is synthesized by fibroblasts, smooth muscle cells, reticular cells and hepatocytes. Forms networks that support very cellular organs or tissues such as the liver, spleen, lymph nodes, smooth muscle, adipose tissue, lungs or skin. They are also part of the basal laminae. Type IV: it is synthesized by epithelial cells, muscle cells and Schwann cells. Form networks to form the basal laminae. Others: at least 35 different types of collagen. They are in minority and serve mainly to establish unions between different components of the matrix.  Elastic fibers relaxed relaxed stretched stretched relaxed 0 Made of elastin protein and also fibrillin. Thin, long and branched fibers. They have elastic properties and provide elasticity to the tissue. astic fibers synthesized fibroblasts bysmooth muscle cells Elastin biosynthesis Fibroblasts Ground substance Tropoelastin polymerization Proelastin + Fibrillin The elastic fibers can be synthesized by fibroblasts and also by smooth muscle cells of the vessels. 1. Fibrillin molecules are synthesized and form microfibrils. 2. Microfibrils are grouped to form a hollow cylinder where the tropoelastin will be deposited. 3. When the molecules of tropoelastin polymerize and bind to fibrillin, they form the elastic fiber. fibrillin microfibers tapqfgit.grpside pffgngigebingtropoelestin Basement membrane Non-cellular interface between epithelial and connective tissue There is a similar structure (outer lamina) surrounding skeletal and smooth muscle cells, adipocytes and Schwann cells It is composed of basal lamina and reticular lamina Basal lamina: - Synthesized by the epithelium - It consists of structural glycoproteins and integrin fractions that attach to the epithelium - Next, there is a mesh of type IV collagen that joins the reticular lamina and will work as a filter for whatever comes from the epithelium to the connective (or vice versa) Reticular lamina: - Synthesized by the connective tissue - Formed mostly by reticular fibers (collagen type III) - Holds the basal lamina to the connective  Connective tissue cells In the connective tissue there are two types of cells: Permanent cells (or resident cells) Transient cells (or wandering cells) The permanent/resident cells are cells that have developed in the connective tissue, they always remain in it and is where they perform their functions. Permanent cells of the connective tissue: Fibroblasts synthesize matrix components Adipocytes Pericytes Mast cells Macrophages FAMMP Connective tissue cells 59dmarrow true go omelette tissue Transient/wandering cells originate mainly in the bone marrow and circulate in the blood. When receiving an adequate stimulus, they leave the bloodstream to go to the connective tissue, where they will develop their specific functions. They are short-lived cells that must be replaced constantly. Transient cells of the connective tissue: Leukocytes WBC Plasma cells  Origin of connective tissue cells Undifferentiated mesenchymal stem cell CAFO Chondroblast Osteoblast Hematopoietic stem cell Adipocyte Fibroblast Lymphocyte Adipose tissue Connective Monocyte Eritrocyte Blood tissue proper Chondrocyte Osteocyte Mast Neutrophil cell Plasma cell Cartilage Bone Macrophage Osteoblast Connective Eosinophil tissue Bone Basophil Blood Mesenchymal stem cells Undifferentiated, pluripotent cells Irregular shape with cytoplasmic prolongations Give rise to most of the fixed cells of the connective tissue Appear mostly in embryonic tissues Do not exist in adults, but pericytes will have a similar function  Fibroblasts Main cells of the connective tissue - the most abundant and most widely distributed cells, elongated cells with ovoid nucleus. Derived from mesenchymal cells. Synthesize most of the connective ECM. When they are inactive they are called fibrocytes (smaller and ovoid shape). There are specialized fibroblasts such as myofibroblasts and reticular cells Teatadfibroblasts Reticular cells Fibroblasts specialized in segregating reticular fibers. Many extensions. Form a network together with the reticular fibers to support very cellular organs.  special type of fibroblast Myofibroblasts Fibroblasts with contractile properties. Appearance very similar to that of fibroblasts Participate mainly in wound healing Also appear in the seminiferous tubules of the testicle  Surround blood vessels canbecomefibroblasts endothelium Pericytes smooth muscle cells Pluripotent cells that derive from mesenchymal stem cells Surround the endothelial cells of the capillaries Under certain stimuli, they can differentiate to another type of cells, especially fibroblasts, endothelial cells and smooth muscle cells.  11MEur largest reason Mast cells antigen Largest permanent cells of the chemoties connective tissue, ovoid shape and central spherical nucleus. Contain numerous cytoplasmatic granules, whose content will be released in the presence of some antigen. They participate in the immune response. Content of the granules: heparin (anticoagulant), histamine (vasodilation, increased vascular permeability, bronchoconstriction, increased secretion of mucus), enzymes and chemotactic factors (attract leukocytes).  formed in blood code asmonocytes Macrophages tissues turn into macrophages Some behave like permanent cells, others like transient cells. Large, irregular shaped cells. Formed in the bone marrow and circulate in the blood as monocytes. When they reach the tissues they evolve into macrophages. Active phagocytes - they participate in the elimination of cellular waste and in the protection against invading organisms.  Leukocytes Migratory cells of the connective tissue Eosinophil They are formed in the bone marrow and circulate Neutrophil in the blood, although they often move to the large tissues, especially during inflammation. multilobed Participate in the immune response. man Phagocytizebacteria - Neutrophils: granulocytes whose granules are not Neutrophil Basophil colored with the usual dyes. Large and with a multilobed nucleus. They phagocytize bacteria. - Eosinophils: Alergic in afightparasites granulocytes whose granules are granula stained with acid dyes (eosin). Usually with bilobed nucleus. They fight parasites by releasing cytotoxins. Monocyte They also regulate allergic reactions. inflammatoryprocesses - Basophils: granulocytes whose granules are stained with basic dyes. Often with bilobed nucleus. They regulate inflammatory processes. - Monocytes: precursors of macrophages. - Lymphocytes: small, rounded cells with a rounded Lymphocyte nucleus that occupies most of the cytoplasm. They are involved in viral infections. viralinfection turn into macrophage Plasma cells Migratory cells derived from B lymphocytes (blood) Rounded cells and eccentric nucleus, abundant cytoplasm Secrete antibodies  Classification of the connective tissue Pericytes inadults Embryonic: – Mesenchymal CT: present in the embryo, contains mesenchymal cells and amorphous ground substance. – Mucoid CT: loose, amorphous connective, with a gelatinous matrix rich in hyaluronic acid, scarce collagen and fibroblasts. It is found only within the umbilical cord and under the skin in embryos. Thinghavemesenchymal stemalls Adult: Connective tissue – Loose CT proper – Dense 199 type collagen fibroblasts 19Tagent b – Elastic – Reticular eating Dense Loose it crype – Adipose t Ere  Loose connective tissue Efi as Abundant ground substance and tissue fluid. Some fixed cells and few fibers arranged loosely and disorderly. Easily vascularized and innervated. Fills the interstitial space of organs, it is located below the epithelia, in the deep layers of the skin, surrounds vessels and the parenchyma of glands.  Dense connective tissue TEE nast Abundant fibers and a few cells. Collagen fibers are grouped into bundles and give a lot of resistance to stress. When the bundles of fibers are arranged in a disordered manner, they form the irregular dense connective tissue. This tissue appears in the dermis, the nerve sheaths and fasciae of muscles and organ capsules.  - When the bundles of fibers are organized in parallel, they form the regular dense connective tissue. It appears in tendons, ligaments and aponeurosis. nuclei of Ligaments fibroblasts ifTendons pink collagen fibers  Elastic connective tissue strongpink are the bundles ofthe fibers Thick bundles of elastic fibers organized in parallel joined by loose connective tissue Present in blood vessels, yellow ligament of the spine and suspensory ligament of the penis. Reticular connective tissue Collagen type111 Association of reticular cells with reticular fibers and macrophages. Present in very cellular organs and tissues: liver, spleen, lymph nodes, adipose tissue, bone marrow